In the manufacture of hollow glass articles, such as drinking glasses, tubes enlarged at their mid portion, for the so-called "oil lamps", etc., once said articles have been formed in the corresponding machines, it becomes necessary to cut the excess of glass of the articles by using cutting apparatuses which are common in the glass industry, same which cut off the excess glass of articles and simultaneously flange the cut portions of these. Once said articles are cut on one or both ends, they are transported to a tempering furnace, where they are relieved of the stress or efforts accumulated along the process of their manufacture.
The cutting systems known at present are composed of a gyratory fastening base, which holds the glass article from its intermediate convex portion or from its closed end; a burner of the gas-oxygen type which heats up glass along an imaginary cutting line, until it makes it reach a melting temperature whereby the excess portion of glass of the article is separated. As soon as the cutting has been done, the burner is left actuated shortly over the cut portion of article so as to flange the same and to provide a finish thereto.
An example of the cutting apparatuses may be found in U.S. Pat. No. 2,334,111 of Nov. 9, 1943, which describes a machine for cutting the spare portions of glass articles. In this case, the article meant to be cut is placed in an inverted position over a vertically reciprocating disk, and subsequently held from its upper end by a vacuum chuck. As the cutting operation is initiated, the chuck and disk gyrate but in one direction, thereby exposing the article to the heat of the burner and, as glass starts to melt, the chuck elevates the article and the excess portion of the article in the disk is then submitted to a force opposite to the initial rotation of the article, thus producing a tensile action which continues with the cutting of the article. At the same time, the top portion of the article keeps elevating until the article is cut according to a specified line.
Another example of the cutting apparatuses is described in the U.S. Pat. No. 2,537,660 of Jan. 9, 1951, which relates to an apparatus for the thermal cutting of the excess portions of hollow glass articles (drinking glasses, in particular), which by means of a chuck by the use of suction, holds the glasses in an inverted position, this is to say, from the bottom, while a article support with moil-gripping fingers holds the excess of glass. During the cutting operation and before glass melts by the action of the burner, the chuck and article support gyrate in the same direction and, afterwards, as glass begins to melt, the article support starts to move downwards gradually, in order to separate the glass in a uniform manner.
Nevertheless, even there are machines for cutting the excess of glass articles, the actual problem with these is that they have not been capable of achieving that the cutting of glass be made in a uniform way, for a "teardrop" always forms at the last point of separation of glass.
Another problem found is that, the principle of causing the article to gyrate, while having a static burner of the gas-oxygen type emit energy for melting the glass, offers the follow ing disadvantage: the mechanisms used for holding and causing the article to gyrate in the burner create certain eccentricity between the article and the burner, thereby causing it to follow a sine-wave trajectory when cutting the excess portion and thus affecting the edge of the article.
A further problem is that, in the machines used nowadays, there is too much separation between the burner and the article, and this causes the thickness of the frame -once the cut has been done- to make the flange of the article thick too, thus leaving much to be desired as to the quality of same.
All of these disadvantages and inconveniences of the previous techniques are totally set aside with a machine which cuts the excess portion(s) of glass articles while keeping these firmly fastened, and featuring a burner with an oscillatory movement on the ends of same. This allows to maintain a constant distance between the burner and the article, thereby making sure that the article receives the same amount of energy all around the perimeter of such article.
Another advantage of this system is that the line of the flame maintains a straight trajectory, while being also possible to set the flame at a shorter distance and reduce the energy applied, thereby producing a thinner cut and one of more quality.
With this type of machine, the formulation of the "teardrop" at the point of separation of article is completely eliminated.